A wide variety of trailers have been developed for transportation of various goods via roadways. Such trailers include platform trailers, refuse trailers, frame and frameless dump trailers as well as other types. In the various trailer configurations, suspension systems are provided in association with wheels of the trailer to provide a smoother ride and facilitate handling and transportation of loads thereby. As it is desired to maximize the load-carrying capacity of the trailer, the characteristics of the suspension system and mounting arrangement become an important aspect of the trailer design.
Prior trailers typically use a steel suspension system which includes steel hangers, steel brackets, suspension arm, air spring, and shock absorbers. The suspension arm is attached to the axle and the air spring; steel hangers, and steel brackets are generally attached to one or more central I-beams or a sub-frame foundation over the rear wheels of the trailer. This poses a particular problem for aluminum trailer frames, as the steel hangers cannot be welded directly to the aluminum frame. To overcome the problem, trailer manufacturers have added a steel attachment plate to the top of the steel hanger and a mating aluminum base plate on the bottom frame of the trailer. The steel attachment plate is then bolted to the aluminum base plate. However, substantial problems still exist. The steel suspensions and additional steel and aluminum attachment plates add a significant amount of weight to the trailer. The steel suspensions are subject to rust, and the dissimilar metal of the steel adjacent the aluminum can result in galvanic corrosion.
In the past, trailers had been manufactured using plates of aluminum sheet welded together and reinforced with reinforcing ribs. Now, some trailers are being manufactured using high strength extruded aluminum plate such as 6061. The extruded aluminum provides great advantages in terms of strength while eliminating much of the need for reinforcing ribs along the trailer body. However, the strength and durability required for many of the subframe and suspension components have substantially prevented the use of aluminum on either a subframe or suspension assembly. Prior art attempts to incorporate aluminum suspension components have either been too complex or too weak to be of any commercial benefit or success. In addition, there has been no option available to retrofit existing aluminum trailers with an aluminum hanger system. Accordingly, these material advantages have not been utilized in the structural components such as the suspension.
It would, therefore, be desirable to provide an aluminum hanger and hanger assembly which has the desired strength characteristics, while being of reduced weight, and which allows for various suspension systems to be integrated into the trailer construction in a simplified manner. It would also be desirable to provide an aluminum hanger assembly for mounting on existing aluminum trailers designed for or having steel hangers.